TripAdvisor and Expedia are the two latest companies to complain to Europe's competition regulators about Google.

On Tuesday TripAdvisor said that "anti-competitive and unfair practices by Google" harm the marketplace and consumer welfare, but didn't give details of the claims. Expedia filed its complaint with the European Commission last Friday bringing the number of formal complaints against the Internet giant to around a dozen.

Google is accused of using its search engine to direct users to its own services and to reduce the visibility of competing websites and services. Expedia says that Google's flight-search service, which was launched last year, "excludes any link to online travel agencies."

Most of the other complaints come from smaller companies, including French search engine eJustice.fr and the U.K.-based Foundem, which first contacted the European Commission in 2010. However, other voices soon joined theirs and regulators extended the case into a full investigation last November to determine whether Google's algorithm unfairly penalizes rivals.

Competition Commissioner JoaquAn Almunia said last week that there would be no ruling on whether or not Google abused its dominant market position until after the Commission's holidays finish on April 10.

Nonetheless rumors abound that the search company will be hit with a long list of objections. Consumer rights organizations have urged the Commission to take a strong stance on the principle of search neutrality.

If Google is found to have breached E.U. competition laws, the Commission will issue a "Statement of Objections" outlining its concerns.

Google will then have a chance to respond and potentially resolve the problems before facing sanctions. If it comes to that, the Commission can fine companies up to 10 percent of their global turnover for breaching E.U. rules and well as imposing conditions on how they run their businesses.

It is estimated that Google has almost 95 percent of Europe's search traffic.